The objectives of this research are to synthesize model compounds of the active and structural sites of Zn2 ion and Ca2 ion metalloenzymes for which the Zn2 ion and/or Ca2 ion have been replaced by Cd2 ion. The 113Cd nmr of these metal-substituted enzymes has been and continues to be an area of active interest. Of particular interest are the enzymes: horse liver alcohol dehydrogenase, carboxypeptidase A, carbonic anhydrase, alkaline phosphatase, superoxide dismutase, metallothionein, parvalbumin and concanovalin A. The crystal structures of these model compounds will be determined and their solid and solution 113Cd nmr will be observed. The Cd2 ion environment from the X-ray data will be correlated with the 113Cd nmr data. These data are essential to the understanding of the 113Cd nmr data of these metalloenzymes and are of fundamental importance for the continued development of 113Cd nmr as a probe of metalloenzyme structure.